Seal raised flower bed?

Hello, first post. Not much experience or knowledge, so go easy :D

I'm planning a project for next spring to build some raised flower boxes from wood. To save money and hassle I planned to use pressure-treated wood. I've read all about the contamination issue, but this is for flowers (annuals), so I'm not much concerned. However, I am concerned about the lifetime of the flower beds. I'd like them to last at least 10 years, and a bonus if the wood stays looking good.

I live in Colorado, so it will see all kinds of weather. The wood will be partially covered by dirt and rocks (in part for permanence, and in part due to sloping ground), not to mention the dirt on the inside of the box. I'm trying to find a low cost, low difficulty way of doing this.

My questions are these: do I need to seal pressure-treated wood to protect against weather? If so, can I get away with doing this once and only once, instead of having to re-seal every 2-3 years? Do I need to look for a certain pressure-treatment rating for this project?

Thanks in advance!

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Seal raised flower bed?

I built several flower boxes over the years. I used cedar in direct contact with soil, the longest one lasted was about 20 years, which was acceptable to me. If you insist on PT, use the variety of PT rated for direct contact with soil. Most PT is not rated for soil contact, but soil rated PT has enough copper to resist the organisms in soil that break down the lumber, and should last at least ten years. No need to treat the lumber. You may not be able to get soil contact rated PT at the big box store, you may need a real lumber yard for this.

PT will start to split almost immediately after construction, as it is typically sold green, and starts to dry quickly. There is nothing you can do about this, unless you spring for kiln dried, soil contact PT lumber, which is available but expensive.

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Seal raised flower bed?

Quote:

Originally Posted by Daniel Holzman

I built several flower boxes over the years. I used cedar in direct contact with soil, the longest one lasted was about 20 years, which was acceptable to me. If you insist on PT, use the variety of PT rated for direct contact with soil. Most PT is not rated for soil contact, but soil rated PT has enough copper to resist the organisms in soil that break down the lumber, and should last at least ten years. No need to treat the lumber. You may not be able to get soil contact rated PT at the big box store, you may need a real lumber yard for this.

PT will start to split almost immediately after construction, as it is typically sold green, and starts to dry quickly. There is nothing you can do about this, unless you spring for kiln dried, soil contact PT lumber, which is available but expensive.

Seal raised flower bed?

Seal the areas that will contact soil (insides and bottom of bottom race) just as you would a subgrade basement or foundation, and yes, do treat the outside with a oil or water seal coat. The contamination of soil and plantings will be minimal and short-lived if you aren't slppy or excessive. Normal watering will carry it off (essentially straight down) not into the potting soil.

Seal raised flower bed?

Quote:

Originally Posted by Daniel Holzman

I built several flower boxes over the years. I used cedar in direct contact with soil, the longest one lasted was about 20 years, which was acceptable to me. If you insist on PT, use the variety of PT rated for direct contact with soil. Most PT is not rated for soil contact, but soil rated PT has enough copper to resist the organisms in soil that break down the lumber, and should last at least ten years. No need to treat the lumber. You may not be able to get soil contact rated PT at the big box store, you may need a real lumber yard for this.

PT will start to split almost immediately after construction, as it is typically sold green, and starts to dry quickly. There is nothing you can do about this, unless you spring for kiln dried, soil contact PT lumber, which is available but expensive.

Good cedar with natural preservatives in the wood is hard (and costly) to find, nowadays. Most will hardly outlast other woods, like fir. Its even more so regarding "redwood", which needs to be oldgrowth and grown in close contact with oaks (for tannin).